Rheostat for electric motors.



J. T. KALWEIT & W. 11. GAULKE. RHEOSTAT FOB. ELECTRIC MOTORS. APPLICATION FILED JULY7,1910.

1,006,560. Patented 0 1. 24, 1911.

h NT 'O N In I I I I I l I I I I I UNITED STATES PATENT, OFFICE.

JULIUS T. KALWEIT AND WILLIAM H. GAULKE, F MILWAUKEE, WISCONSIN,- ASSIGN- OBS TO INDEPENDENT ELECTRIC MANUFACTURING- COMPANY, A CORPORATION OF WISCONSIN.

RHEOSTAT FOR ELECTRIC MOTORS.

Application filed July 7, 1910. Serial No. 570,915.

, To all whom it may concern;

Be it known that we, JULIUS T. IQKLWEIT and WILLIAM H. GAULKE, both of Milwaukee, Wisconsin, have invented a Rheostat for Electric Motors, of which the following is a specification.

This invention relates to rheost-ats or reslstance-boxes for electric circuits, and more particularly to that type called startingboxes, which are used for starting and controlling electric motors. This type of rheostat is provided with a quantity of resistance which is divided into sections by taps leading to contact-pieces on the face of the box, over which moves a pivoted contact-arm which is connected with one pole ,of the circult, and said arm is provided with a spring acting to bring it back when released to the starting-point, while an electromagnet is arranged in the motor-circuit and acts upon the armature carried by said pivoted arm to hold the latter in on position when it has been turned up to the last'point, in' which all the resistance is cut out of the circuit.

Our invention has for its object to improve the construction of such startingboxes; first, by providing an improved construction of containing-case for the resistance which will completely inclose it so as to prevent danger from flashes in the case of the box or resistance burning out, and at the same time give ample ventilation; secondly,

by providing an improved construction of the contact-pieces, which will make not only a cheaper construction but will enable them to be readily removed and replaced when worn or burned out, without removing the box from its place, thus eliminating time and expense for repairs; thirdly, by providconnection with the accompanying drawings,

Specification of Letters Patent.

'9 are perspective views of separate elements the ends of the plates B (see Fig.4),tl1're-fi Patented Oct" which show the most improved form lnventlon as applied to one of the siriall sizes 4 I of rheostat, It will of course be understood that in larger sizes theform and-number ofc parts will be varied as reliuired by en e A stances while retaining the same principle.

In the aforesaid drawings Figure 1 is a fio fil front elevation of a complete rheostat con st-ructed according to ourinvention;

is a plan thereof, with apart of the upper guard-piece of the casing broken away; Big-i 3 is a vertical transverse section onplanej with the contact-arm in vertical position, one

of the resistance coils being shown in pa tia section; Fig. 4 is, as to the upper'halfi' a' front view of the rheostat with the front plate removed, and as to the lower half, section on'the plane 4. Figs. 5, 6, 7, 8,'and

and Fig. 10 is a diagrammatic view of'the electrical connections.

In these drawings every referencel'ette refers always to the same part," i

The rheostat-resistance as shown comprises a series of coils of resistance-wire'A mounted upon tubes a of insulating'material (.su'c

as asbestos and said tubes are mouuted'on 0 insulating spindles a which have two tape-r ing ends separated by a flange; the outer ends of the spindles of each coil being-in turn supported by two holding-plates "B. which close theuppds ofthe casing and have a series of holes b in which the outeritap ei ing endsa of said spindles fit.

The body-member'C of the casing or box); comprises only. the two lateral sides and t1 back thereof, the ends and front thereof;

being open; and at said ends there are pro Y vided overhanging flanges c, which engage by holding them and the coils A in position,

and at the same time closing the endsof the 951 0 box, The front of the box is closed by the insulating slab -D, which, as customarily,

may be made of any suit-able insulating ma-1 slab is secured in place by four screws 'tZ slab and through corresponding holes" c in the back of the casing C, said screws serving also to fasten four foot-pieces -E WlllClI are-:1

set between snugs 0 .on the back of thescasing and secured by the nuts 03 on the, endsof a at, rear i i able to pass through the holes f with a series of holes 79 which provide for said screws. These foot-pieces, however, are i not of the essence of our invention, but form a convenient means of supportingtherheostat on and securing it to a wall or switchboard. I

. In order to secure ventilation for the interior'of the box, each plate B is perforated air-currents through the box; and to detain any particles of hot metal which may be blown through these holes, as in the case of a short-circuit or burn-out, each end of the box is covered with a guard-piece F, whose ends are flanged and secured to the flanges c'by screws f; each, of said guard-pieces interlocking with the back edge of the member C by means of a rabbet 7, but at the front a series of apertures f are provided through which the air-currents can pass. Any material which may possibly be blown through the apertures b will strike the interior of the guard-pieces F and will not be Upon the face of the-slab D are mounted, among otherthings, a shoulder-pin G, which forms a pivot for the contact-arm H, and a series of contact-plates I, arranged about the 3 pin G as a center and electrically connected to the several sections of resistance and to 1 other points, as will be hereinbelow del scribed. The nature and construction of said contact-arm and plates form important features of our invention. e provide each contact-plate in the form of a metallic strip, ordinarily of brass, made in the forinshown in Fig. 6, with holes 2" and 2' at its opposite t ends.- A series of screw-stems J, carrying are set in corresponding holes in,

nuts 7', y the slab D and secured in place by said nuts; the outer end of each screw-stem passing through the hole iin one of the contactplates, which is secured thereto by the outer nut 9', while the inner nut j is used for securing one or more wire-leads from the resistance-sections A. At the inner end of each contact-plate I is set a shouldered dowel K, one end of which fits in the hole 2' and the other in a recess (Z in the face of the slab D, i said recess being such as to form a driving fit for the dowel, or else the dowel may be fixed therein by use of cement or other ad- 1 hesive. As thus constructed it will be seen that when one of the plates I is injured or worn out, it can be removed and replaced by a new one in a very few minutes, and at a i very trifling expense, by simply releasing the outer nut j. 1 t

The contact-arm H ispivotally mounted i on the pin G as aforesaid, which latter is t provided with a spacing-shoulder g and a nut 9 by which it is secured in a hole in i the slab D and electrically connected with i one of the terminals of the box as hereinafter described. Said contact-arm is conveniently made from two metal bars k 1 P on the contact-arm.

secured together by rivets in, 72 72- The pivoted end of the bar it is separated from that of the bar 71 in order to give a proper lateral bearing to provide for the .pressure of the arm against the contact-plates, and in order to move the arm when released to the left-hand or eff position and hold it there, a helical torsion-spring it is mounted upon the pin G between the ends of the two bars, one end of said spring being engaged with the arm and the other with an abutment-pin or screw 7& mounted on the slab D. A suitable abutment-pin L, provided with a rubber sleeve Z for a cushion, is placed in position to limit the left-hand swing of the contactarm. On the outer end of the arni, or at any convenient point thereof, is mounted the handle it upon a screw h At a point opposite the contact-plates I a slot k is formed in the contact-arm to receive the contact-block M, which can move forward and back in said slot and thus adjust itself to any unevenness of the plates and press with a continuous and even pressure thereupon. The lower bar it of the arm is bent in as shown at h (Fig. 3) away from the bar 7& at this point, so as to give a wide lateral bearing to the contact-block.

Upon the latter presses one end of a member N, whose other end rests on the head of the rivet 7L and upon which resiliently presses a helical spring a mounted on a threaded pin 02, which projects at right angles to the arm H and carries on its end nuts a whereby the pressure of the spring may be adjusted and fixed. The arm ll itself being connected in a circuit, a positive and unvarying electrical connection with the contact-block M is provided by a flexible connecting-wire m soldered to the block and engaged under the head of a binding-screw m.

The electromagnetic means by which the contactarm is held at the right-hand or on position comprises an eiectromaguet having a cylindrical core 0 projecting slightly from the end facing the contact-arm, 1 said magnet being mounted upon a base 0 which is in turn mounted on the slab D, and which has an angular flange 0 to which the core 0 is secured by a screw 0 and which forms a complemental core, as its end 0 is 5 flush with the end of the core 0' and coacts therewith, to attratt and hold the armature This armature magl I a netically connects the core 0 and the end or the flange 0 when the contact-arm 18 111 its right-hand or on POSltlOIl and is pivoted at 1ts end farthest from the pin G upon the i rivet its, this giving it a slight swinging 1 movement, whose extent is llltllCiltQtl bythe fulland dotted-line positions shown in Fig.

1. As clearly illustrated in Figs. 2 and 9,

said member P has a flange or apron ppr allel to the lateral edge of the contact-arm and adapted to form a suitable surface for I the. armature pivotally, but the pivotal.

engagement with the magnetic elements;

and 0 a Heretofore it has been customary to mount point was placed midway between the mag netlc poles. But one of said poles, namely 7 the pole 0, is very muc-hstronger than the other, because the" whole magnetic flux passes through the pole b, butonlya part this in View through the pole 0 Having we have placed the pivotal point of the armature P closer to the former than to thelat'ter.

consideration We have placed the pivotal point 71, beyond both magnetic poles, and we have found by experiment that-when thus mounted the magnet-strength which is required to hold the arm is only about half that which is required when the pivotal point is placed'midway between the points 0 and 0 The manner in which the several elect-rlcal I elements of our rheostat are intended to be connected up to each other and to a shuntmotor and line-circuit isillustrated in Fig. 10." .Three terminals Q, Q and Q are mounted on the slab D; thefirst Q, being ermanently connected to the arm H and intende'd to be connected'to one line-wire 1-; the second, Q being connected with the right-hand or on contact-plate I, and intended for connecting one pole of the motor-armature thereto; and the third,

Q being connected through the electro-' magnet Oto the last active contact-plate I on, the left, and being intended for connection with one pole of the motor-field T. It will be observed that the'terminal of the magnet coil is grounded upon-the armaturebase 0 whereby. as soon as the arm has reached its on position the armature coils are out out of the circuit.

QYhile we have hereinabove described tne understood that-we do not limit ourselves to L anyone of the particular features thereof;

,n. fully realize that it is capable of numer- ,"Kins?"modifications, and we consider such -modifications ,and omissions may be made without departing from the principle of oul."

' 6 invention.

Having thus described our invention, What weclaim as new and desire to secure by Letters Patent is:

1. In a device of the character described, the construction for a'contact-piece which comprises, in combination with the insulating slab, a screw-stem passing through. a hole therein, nuts on said screw-stem on the opposite sides of said slab securing it in position,

slab

referredform of our invention, we wish it an oblong contactplate having a hole in one end through which the projecting end of said screw-stem passes, a nut on the end'of said screw-stem .over said contact-plate, said contact-plate having also a hole at its oppothe combination with the insulating slab and. the pivoted contact-arm of a row of contact pieces arranged upon said slababout the pivot of said arm as a center, each of said contact-pieces being an elongated metal plate .70 .site end, and ashouldered spac1ng-p1n fixed- 1 havinga hole at one end thereof, a row of screwstems mounted on and projecting from the front face of said slab, spacingfpieces on the respective stemsadjacent to the slab, the several stems passing through said holes in the respective plates beyond said spacingpieces, nuts on the respective stems over said plates and holding them in position, and

means for supporting and holding against lateral'movement the opposite ends of said plates.

3. In a device of the character described, the combination with the insulating slab and the pivoted contact-arm of a row of contactpieces arranged upon said slab about the pivot of said arm as a center, each of said contact-pieces being an elongated metal plate having a hole at each end thereof, a. row of screw-stems mounted on and projecting from the front face of said slab, spacing-pieces on the respective stems adjacent to the slab, the several stems passing through the holes in one end of the respective plates beyond said spacing-pieces, nuts on the respective stems over said plates and holding them in position, and a row of shouldered dowels permanen fixed in recesses in the face of said 1e ends of which fit in the holes in the opposite ends of said plates.

4. In a device of the character described, the combination with a pivoted contact-arm formed with a slot therein, of a contactblo-ck fitting in said slot and having aibackand-forth movement, contact-pieces opposite said arm on which said block presses, a bar resting at one end on said block and at the other end on said arm, a screw-stem mounted on said arm and passing through a hole in said bar, a coiled.compressiomspring mounted 011 said stern,- and a nut mounted on the 5. In. a device of the character described,

a construction for a contact-piece which comprises, in combination with the insulating slab, a flat contact-plate having a-hole in each end, a pair of corresponding holes in said slab, a dowel-pin fitting in one of said holes in the slab and in one hole in the contact-piece, and carrying a spacing-eh.

m'ent separating the cpntact-pieae from the slab, and ascrew passmg through the other hole in the contact-piece ancl that in the slab and securing the contact-piece t0 the slab, said screw carrying another s'pacing element similar to the first, whereby said contactpiece is held parallel to and Spaced apart from said slab,

JULIUS T. KALWEET.

WILLIAM 'H. GAULLUE.

lVitnesses GEORGE W COLLE, FLORENCE M. MALLON. 

